Method of manufacturing smokeless powder



Feb. 22, 1944. MACKEY METHOD OF MANUFACTURING SMOKELESS POWDER- Filed March 27, 1940 19,7/Hm /Mam ATTORNEY Patented at. 22, 1944 METHOD OF MANUFACTURING SMOKELESS POWDER Bill Harry Mackey, Wilmington, Deli, assignor to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware Application March 27,1940, Serial No. 326,162

fl Claims. (CI. 18-55 This invention pertains to a process of making smokeless powder and more particularly to'a smokeless powder-in the form of grains having definite dimensions, said powder possessing enhanced mechanical strength.

The chief advantage of producing powder grains of predetermined size and shape, and having perforations of exact size, lies in the fact that such grains permit some control over the burning of the ppwder and consequently over itsballistic performance; Thus, the perforations of any particular grainare designed to afiord an I increase in the burning surface as the grain burns, and hence are deemed an important factor in maintaining what isconsidered the optimum burning surface during the various stages of the 4 preciably.

single direction only. Thus, although many dies involving various modifications with respect to 5 their assembly have been known, all of them permit a substantially straight flow of the colloid along the pins of the die plate and the walls of the die body. Such a conventional die is indicated in several figures of the drawing referred to in the following. After issuing from the con ventional die, the strings of colloid are fed to cutters adjusted to ,cutsegments of the desired length. The green" powder grains are then treated in asystem which permits the recovery of the bulk of the solvent, following which they aredried.

The resulting conventional powder grainsinvariably have exhibited two outstanding defective characteristics: First, the grain has'shrunk much more across the diameter or web thanit has in length; second, upon impact the grainshows a cleavage along aline parallel to the longitudinal axis of the grain rather than'across its-diameter.

-Such characteristics are undesirable for the reason that the proper ballistic performance of a powder is dependent upon the grains remaining' as integral units during the combustion of the charge, rather than breaking into fragments, since fragmentation of said grains exposesbuming surface exceeding that calculated as desirable, with the result that erratic ballistic performances are obtained. Actually, such erratic performances heretofore have been common, at

least in certain firearms, the fragmentation of the grains resulting either from the pressure created by the medium of ignition or bythe pressure developed by combustion of part of the smokeless powder charge itself.

Various attempts have beenmadeto overcome this undesirable phenomenon, said attempts bee dimensions.

ing directed to acomposition better ableto withstand the pressures developed, as well as to charges of such design that fragmentation would be less aptt'o occur. Thus, ;in order to obtain a tougher composition, varying amounts of guncotton and pyrocellulose have been-blended, different solvents have been employed, and numerous additional ingredientshave been. incorporated in the composition. Likewise, experiments have been made wherein the powder charge was arranged with respect \to the ignition charge in order to prevent travel of the charge, as by spacers, for example; so that fragmentation a would be eliminated oi at least diminished ap- The foregoing mod cations have in general effected an improvement but in no case can the conventional powder be fired with the certainty that fragmentation and consequent erratic ballist-ic results will be avoided.

The object of thepresent invention is a method of pressing smokeless colloids which yields agrain that shrinks substantially uniformly in all Other objects will become apparent as the invention is described hereinafter.

I have found thatthe foregoing objects are accomplished by forming the smokeless powder grain insuch manner that there is a random or improved orientation of the particles of material of which the grain is composed...

This may be accomplished by more than one method. For instance, I have found that the two undesirable characteristics mentioned, namely, the uneven shrinkage and extreme frangibility can be overcome throughthat improved particle orientation achieved if, while formingare notsaligned in one direction only,- but rather point in numerous directions, lying at ,various angles in many diiferent planes. This dismay of particles I call random orientation and this term is used in this sense throughout the description of the invention. The grains wherein Y the particles have this property are characterized by uniform shrinkage and greatly enhanced imconcentric path, namely, by charging the colloid into die molds and applying pressure preferably by means of a piston to form the grain of predetermined dimensions.

My invention may be more readily understood by referring to the accompanying drawing. Similar numerals are employed to designate corresponding parts throughout the various figures of the drawing.

Figure 1 is a cross-sectional view in elevation of a die mold according to the present invention. Figure 2 is a cross-sectional view in elevation of a die according to the present invention. Figure 3 is a plan view of the same.

The following example refers in greater detail to Figure 1 of the drawing. This example also brings out the outstanding properties of the powder of my invention.

I Example A smokeless powder colloid was prepared in conventional fashion, the various ingredients being mixed with. the requisite amount of ether and alcohol. After mixing;- the colloid was macerated, pressed into a block, and the block extruded through small orifices, thereby forming the material into stringss A portion of these strings was pressed in a press and extruded through the conventional type of die.

-The second portion of the colloid was divided into predetermined die molds of the type shown in Figure 1, wherein It) represents a die head having the die pins ll, said die head fitting snugly. within the walls l2. Pressure is applied by appropriate means via the piston l3.. The particular die molds employed were designed to yield a grain having dimensions identical with those produced above. .Both types of grains were dried under identical conditions.

In this manner, grains having identical form and shape were produced, the only diiference being in the actual formation of the final grain. After all the grains had been dried to the same content of volatile material, they were measured to determine the shrinkage of the various dimensions. The amount of shrinkage as determined from the measurement of numerous grains is given below:

4 Grains I Shrinkage 7 Percent Length 4.10 D A (grams formed in usual manner) quantities and charged into increase over the ordinary powder grains, even though the design and composition of the .grains Weight of Distance Grains falling required to metal crack grains Pounds Inches A 0.5 26-30 1 No breakage69" max. ht. 1 Some grains failed to break when the weight was dropped from the maximum height of 69inches.

In conducting the impact tests on the A grains, it was noted that the grain cracked almost invariably along the longitudinal plane regardless of the position in which the grain was placed. Whether it .was placed with the cross-section uppermost or to one side made no difference. The line of cleavage generally was clean-cut and definite. By contrast, the B grains broke irregularly in a jagged line along no partiqilar plane. The fact that the B grains are much more resistant to impact is shown by theresults cited above, said results indicating that this type of grain has about 5 times the impact resistance of the usual grain.

.The method or means of procuring random orientation is not limited to the molding of powders by means of a device of the type shown in Figure 1, but may be obtained in numerous manners. For instance, referring in greater deonly one series of orifices is shown (Figure 3) fit is clear that more can be added if desired. Undoubtedly, other modifications can be made to cause the material to flow helic'ally or concentrically through the die in orderv that no substantial alignment of the particles in a single direction results.

Figure 4 is a view, partly in cross-section and partly in perspective, of a string of powder as it is formed when using a die of the type set forth in Figures 2 and 3. It may be seen that the particles of the smokeless'powder colloid, due to the direction in which they are forced into the die, take a path which is helical or concentric, so that the string of powder is composed of particles which have not been aligned in one direction'only, because, in moving through the die, they are forced therethrough in a tortuous path which may be indicated by the fine lines,

thoroughly mixed, macrated. compressed in a blocking press, and then extruded through small orifices prior to its extrusion in final form. Due to this rather extreme treatment, it commonly and in many cases to eliminate the fragmentation of smokeless powder charges which obtains ture content.

' csni'rrrcs'rs or conxscrron.

performances due to the fragmentation maybe 7 proportionately reduced or eliminated. Likewise,

the adoption of grains of this type obviates the was believed that the fibrous structure of the necessity of exercising some of the precautions nitrocellulose had been substantially destroyed heretofore taken to keep fragmentation to the and that the colloid was essentially homogeneous. minimum possible degree, such as spacing of the Therefore, it was natural in the absence of excharge, for example.

planation to consider the non-uniform shrink: It will be evident to those skilled in the smokeage and the definite cleavage along the longituless powder art that the foregoing description dinal axis of the grain as inherent characteristics permits of variations without departing from the of smokeless powder. I spirit or scope of the'invention. I intend there- Ihelieve that, even though the colloid be homofore to be limited only in accordance with geneous and composed of particles indiscrimithe following patent claims: nately disarrayed prior to formation of the grain, is I claim: the passage through the usual die causes sub- 1. A method of producing smokeless powder stantial alignment of the particles of the colloid in grains having enhanced resistance to fragmentaone direction only, this direction being that along tion, which a'comprises imparting a helical flow to vthe longitudinal axis of the grain. The force the smokeless powder colloid while extruding necessary to' separate the particles is than less 2 said colloid through a die. than that required to break or sever the particles] 2. A method of producing smokeless powder in a direction cross-wise to the longitudinal axis. grains having enhanced resistance to fragmenta- Thus, it is logical that the elimination of the tion, which comprises forcing said. colloid through solvent by drying would cause greater shrinka helical path during extrusion of smokeless powage across the diameter than in the length 01" der colloid through a die which is adapted to the grain. Likewise, this would account for the yield a finished grain of the definite dimensions. cleavage of the grain along the longitudinal axis 3. A method of producing a substantially uniof the grain. However, I am unable to prove form shrinking smokeless powder grain having conclusively the foregoing explanation and since increased resistance to impact, which comprises it is a theory, I do not intend to be limited imparting a helical path to the colloid while exthereby. truding said colloid through a die of predeter- At any rate, regardless of theory, it is clear mined form. that the methods of my invention as described 4. A method of producing a smokeless powder herein produce a novel form of grain smokeless grain of enhanced resistance to fragmentation, powder. characterized by the fact that the indi- 5 which comprises minglim the various ingredients vidual grains are uniformly shrunk and are re including. nitrocellulose with a solvent for said markably resistantto impact. nitrocellulose, forming the solvent-laden mix- By producing a powder having an impact 'reture into a colloid by exerting work thereon; passsistance much greater than powders of similar ing said colloid in .a helical path while forcing it design n mposition, it is possible to decrease 4 through a die adapted'ito yield the final form of the grain, and drying the grains to a given moisnrnn HARRY MACK EY.

Pate nt llo. 2, 12,201 g February 22, 'i9ld BILL mm mm.

It is hereby certified instep-or a'ppears in the printed specification of above ea Intent requiring correction as follows: Page 3, first column, line l, for "macrated' read --maoerated--; and second column, line 3 01811112, o "said" read -smoke1ess powderand that the said Let- Patent he l ibereadwith this correction therein that the same may conform to the record of, the oase. in the Patent Office. I Siaaedancl se aled this l6th'dsy or na -A. n. 19bi r I Leslie Frazer (Seal) Acting commissioner of Paten'ts.

, cmi'xncm: a? conmcmion. Patent No. 2,3h2,20h.. 1 I February 22, 191d;-

v mm mm mm. Y It 15 hereby certified thateg'ror appear; in the printed specification of the above numbered requiring corbeetioz; 1! follows: Page 3, first whim, line 1, Ib'r 'mcfeted reed --meereted-; and'aecond column, line 23', claim 2, for "eaigi' i-ead --emoke1eae ponder-3 end that the said Lettern Patent shquldlteread with this qorrecti ontherein that the same may conrom to the record oiflthe eue. in the Patent Office.

Sigzedend eeylled m1; l6th'duy or m 1. 9'. 19m. v

- v. V Leslie'Frazer (Seal) 1 an; Cein'miaei'oner or'raten'ta, 

